An angular position sensor, as an important sensor device, is widely used in the automobile and other electromechanical control fields. How to broaden its linearity range and improve its linearity has always been a subject those skilled in the art are dedicated to. A commonly used angular position sensor uses a magnetic induction element to detect the magnetic field variation, which is then converted into the electrical signal output corresponding to the angular position. In order to improve its output linearity relative to the rotation angle of the measured object and broaden the linearity range, those skilled in the art have done a great deal of research, and obtained various design proposals about the magnetic circuit.
For example, the American patent specification U.S. Pat. No. 5,861,745A disclosed on Jan. 19, 1999 presents an angle measurement device, which obtains the complete linearity range bigger than 180° by making use of a radially magnetized ring magnet that rotates together with the measured object. In this solution, however, the wider the required linearity range is, the bigger the ring magnet will be, thus increasing the cost of raw material; besides, the magnet material is more difficult to be processed than other metal materials, especially the more complicated ring magnet that is adopted in this solution, whose accuracy is difficult to be guaranteed during processing and positioning, which will increase the processing cost in the production process.